With XHTML namespaces, should each attribute have a namespace too?

Question

When extending XHTML for a very simple CMS, I'm wondering if I should use

<cms:include document="foo/bar" />

or

<cms:include cms:document="foo/bar" />

Given a document declared as follows:

<html xmlns="http://www.w3.org/1999/xhtml" xmlns:cms="http://spongegroup.com/ns/cms">

(basically the idea is to make a simple parser that white-lists a few XHTML tags, and adds a couple of my own).

Is the cms: prefix needed on attributes of an element that is already in the cms: namespace?

ChrisJ · Accepted Answer · 2011-12-06 09:38:49Z

3

You do not need the cms: prefix on the attributes of cms: elements, because the meaning of these attributes is determined by the element they belong to.

See the XML namespace recommendation: “the interpretation of unprefixed attributes is determined by the element on which they appear”.

Technically speaking however, unprefixed attributes belong to the null namespace.

Answer edited on 2011-06-06 to correct a misleading sentence. Thanks to the commenters.

edited Dec 6, 2011 at 9:38

answered Mar 18, 2011 at 20:38

ChrisJ

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5 Comments

Alohci Over a year ago

"By default, the XML attributes of a given element belong to this element's namespace". That's either wrong or misleading. Unprefixed attributes are always in the null namespace, not the XML namespace of the element to which they belong. What the quote you give means is that the attribute is sufficiently qualified by the element to which it belongs, not that it adopts the element's namespace. You are correct that the attribute does not need to have a prefix or namespace assigned to it.

fazy Over a year ago

Thanks guys... seems like a subtle distinction to me, but it's good that I don't need the ns: prefix on every attribute.

Adrian Mouat Over a year ago

Downvote as the answer is simply wrong - please rephrase. Alochi is correct; attributes are in the null namespace by default. Not being aware of this will cause serious problems when trying to use things like XSLT.

ChrisJ Over a year ago

I partially rephrased the answer to correct the misleading sentence.

Adrian Mouat Over a year ago

Ok. I still wouldn't use the phrase "sufficiently qualified" as it will be confused with "qualified name" when what you really mean is "disambiguated" or something similar.

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